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MG MGA - Felt Block above radiator

On particularly hot days my MGA 1600 over heats, although it hasn't boiled the the temp gauge has been close to 230 deg.. MGA Guru recommends fitting felt blocks above the radiator header to prevent hot under bonnet air from leaking over the radiator and then being sucked through the radiator. Has any one fitted this mod and did it help? I see NTG have them available, how are they fitted? Thanks.
John Stephens

John

They are standard items, not modifications. Made of horsehair. Glued to the underside of the bonnet.

Steve
Steve Gyles

Assuming your temp gauge is near accurate you may be better dealing with the cause of the engine getting so warm.

There can be a few causes but if all ease is running well then it might be the cooling/heating system as often this is not fully dealt with considering the decades of existence.

Cleaning out or even draining the engine block is often overlooked, or might not have ever been done, and a lot of crud can build up there (behind the drain tap too) reducing the efficiency of the cooling system and possibly causing hotspots. Same with cleaning the radiator inside and out.

John if you want to email me I'll send you my very simple but basic method of thorough cleaning, it's for a 1275 midget but easily adapted and suitable for most classics, it's been used on 1500 Midgets and Bs successfully, well its so simple and basic it would but it's also thorough which is often missed. You can do part of it or all of and even go on to the more thorough method if suitable, any of it that you do will help.

After you can decide if you need or want to add the felt blocks, they would help anyway but they won't clean the cooling/heating system or get crud out of the block, rad, heater matrix or rest of system. Where you can see it the coolant can look clean and clear but that doesn't mean the whole system is.
Nigel Atkins

John, Barney's site has info regarding this seal as well as other cooling tips; here's the link:

https://mgaguru.com/mgtech/cooling/cool_101.htm
Nick Kopernik

John
Been there and got the T-shirt.

It can do absolutely no harm in fitting the felt block, as Steve says, it is supposed to be there and not difficult to fit.

I reckon over heating is one of the most common discussion points amongst MGA owners - at least among those of us with the original set up.
There are lots of factors that can cause it. Nigel is right that a good clean out of the cooling system can help.
Others will suggest you look at your radiator's condition and in particular, the type of rad you have. But there are lots of other things e.g. thermostat not opening properly.

Do you find it over-heats when in traffic (i.e. stationery or when moving slowly), or when at higher speed?
If it is one or the other, that can give some clues where to look.
Graham
Graham V

.....don't get me started on cooling! Sufficient to say in the sort of hottish weather over Easter my motor stayed quite happily at its 180 to 185 ish.

Steve
Steve Gyles

180 to 185 degrees Steve?

Does this mean that you are now no longer included in the endangered "Cool Runners" sub-species who always ran at 175 degrees or less, regardless of ambient temperature? :-)

Anyway Steve, you are very welcome to join our 180/185 degrees F "Real-World" majority group! :^)

I have occasionally thought about fitting the felt bonnet pad but I have never really had any overheating issues and so it is a the bottom of my "to-do" list for now.

Cheers
Colyn
(PS the capital F above, that preceeds "Real-World stands for Fahrenheit and is not a shortened expletive :-)
Colyn Firth

I totally agree that there can be different causes and a combination and permutation of causes and adding the felt blocks would help anyway.

I think most servicing and maintenance and many repairs boil down to cleaning and lubricating.

The coolant acts as lubricating for the system so it wants to be in good condition and certainly unspent. Many seem to go with the idea that the anti-freeze part still works so it doen't need changing missing the point of the coolant and other properties.

Also just always doing a straight cold drain from the bottom hose (or rad drain tap) is really a minimum and leaves a lot of existing coolant (and muck/rust/crud) inside the system which also dilutes the fresh coolant and its effectiveness. Compare the quantity of fresh coolant you put back in to dry fill capacity.

You do also often need to be careful to treat the temp gauge as just a gauge rather than a spot on accurate instrument (unless it has been absolutely proven to be so) and allow for the same when making comparisons to others. IF all else is running well then take the positions of the needle as being the normal range for the car and only worry if there's sudden and/or wide variance from that norm.

What are these C and F numbers, my car's gauge only has C, N, and H markings and those are enough to worry me and others (Midget 1275). :)
Nigel Atkins

I think if the felt block wasn't a necessary part of the cooling system, the factory wouldn't have bothered putting it there in the first place. Even my 2017 pickup truck has a seal between the hood and the upper radiator shroud for the same reason.

Certainly if you are having cooling problems, lack of the block is unlikely to be the only problem or even the most significant one. But it's also not really accurate to consider it as not part of the root cause, if you are missing that piece of the originally designed cooling system.

I will second Graham's comment about the condition and type of radiator. In all of the MGA cooling problem discussions, the most common theme seems to be replacement radiators that are not made with the same type of core as the original units, and the newer ones are not usually better.

-Del
D Rawlins

Colyn

I used the word 'ish' because with my 7-blade asymmetric fan the temperature changes seem so much more instantaneous on the instrument than I used to see previously. I can watch the thermostat opening and closing quite noticeably even when thoroughly warmed up and on the cruise. The upper end of my temperature range is in slow moving or even stationary traffic. The lower end still happily sees 175.

I am in agreement with all the comments above: clear waterways throughout; and as close to original core design radiator. That's how they came out the factory and it worked. In my opinion for ordinary UK road use every other add on extra is unnecessary to keep her cool (including my fan - but it's more efficient and effective than the metal version). e.g. oil cooler, electric fan.

Steve
Steve Gyles

Mainly driving in the north and getting few jams I have only been concerned with engine temp a couple of times, and on these occasions fuel vaporisation was my main concern, but a couple of points.

The issue isn’t just because of age of engine but I believe there is bigger cooling load with modern petrols as discussed in the MGCC articles. So we may have to improve on original.

I don’t have the horse hair fitted but a bodge I thought I would test a few years ago. It is a section of a Halford’s dense foam kneeling mat. Seem to do job and is still fitted but dirty orange foam is hardly concourse!

By the way one of my getting warm incidents was when I had same excellent radiator core fitted as Steve so it isn’t totally the holy grail. Although I do agree it is probably best available. Bob West is source.

Changing subject slightly I hope for reduction in albeit rare fuel vaporisation incidents as I have over winter fitted bilge pump to force cool carbs..

I seem to remember Barney saying don’t worry too much about elevated engine temps.

Generally I agree with everyone get everything up to spec. Good luck

Paul
Paul Dean

Generally in agreement with everything said about root causes of overheating - wrong radiator, build up of crud in the cooling system, ignition timing, etc. But in my opinion the last thing to think about is the felt block being missing - fitting one is sensible but on mine (twin cam engine so plenty of heat there) it makes no discernible difference to coolant temperature. John, I would be looking at all the others things first to cure an inherent overheating engine.
Good luck.
Bruce.
B Mayo

Perhaps John Stephens could give us some background information and we could help him more specifically.

Steve
Steve Gyles

Hi All.
My A Coupe has a habit of getting hot in traffic but comes quickly down to 180 ish once moving again. My Moss catalogue says those felts are no longer available. Is this out of date? I am wondering about fitting a plastic 6 bladed fan I have in stock. I am not sure where it came from through. Has any body the diameter of the fan,so I can check my fan is appropriate. I have various Sprite parts in stock so it might be from one of those.
Thanks
.
s page

Simon,
if the fan is yellow plastic then it could be for the Spridget (x-flow rad), I think it might be 10" but no longer have one to measure to be sure. I run with electric fan only for better (winter) warm up and with no over ride switch!).
Nigel Atkins

My 7-blade asymmetric fan is approx 12" diameter if that helps. Being 7 blade and oddly spaced, no 2 blades are opposite for a precise measurement. Brilliant thrust from it, probably 30% more than the standard MGA fan.

Bought it from Moss. Part No. AHH6999Z Listed for the MGB. It's in my 5-bearing 1800. The thing you need to watch for is the length of your water pump to give fan clearance with the radiator. I have a short shaft pump.

https://www.moss-europe.co.uk/fan-cooling-7-blades-plastic-ahh6999z.html

Steve
Steve Gyles

With fans they do need to be the right distance from the rad and be the fitted the most efficient way round.

A smoke test will show which way and how much smoke/air is going where (but not how hot it is).
Nigel Atkins

This is my solution, seems to work ok.


AR Terry

Hi, thanks all for your advice. I'm about to flush the system and wondered if there is a water drain tap on the engine block on a 1600 MGA? If so where is it? Thanks
John Stephens

Petcock is just to the left of the dizzy. Once opened, you may need to use a stiff piece of wire to clean out any debris which may prevent the coolant from draining.


Nick Kopernik

John,
you'd be best removing that drain cock all together and poking a bent bit of stiff wire behind around the aperture at drains and flushes to get at least some of the crud that'll be behind there. Just opening that little tap will not give a good flow rate for flushing, coolant, crud, cleaning and flush fluids and the larger aperture will allow for more back-flushing through the block.

I go drain, (fit drain plug), refill with cleaner and clean, drain, flush, back-flush and final flush.

I made up a copy adapted to MGA of my simple but thorough coolant cleaning method(s) which a few owners have found effective, email me if you want a copy.

Nigel Atkins

I believe it is pretty common to never be able to get anything out of block drain plug whatever you do. I can’t remember who but some established authority told me about not to bother about it.
Paul Dean

I disagree, it is worth a try.

If you get some flow then you will get some crud and existing/old coolant out and movement of coolant. It also allows for reverse-flushing which cold loosen and empty out more crud. A hose of (low) pressured running water going both ways will carry out crud and clean to some extent.

If you have coolant that you change every two years you could do this to that drain area every two years and you might get it a little more freed up but I wouldn't bother as I accept the limitations of this operation, just with the regular coolant service the draining of this area and change of coolant should stop further build up and the draining flush out the loose bits.

I don't live on fantasy island and expect one lot of a bit of poking around in the area with draining, cleaning, flushing, reverse-flushing and flushing and then every two years drain and refill with fresh coolant will totally clean the internal tubes but it's not hard work to do initially and doesn't add much time and effort to regular service coolant changes to drain that area.

When most people who bother to try to do this area they are usually surprised how much crud does actually come out.

Paul I hope your established authority wasn't a Cardiologist. :)
Nigel Atkins

I agree with Nigel. When I rebuilt my 5 bearing 1800 before fitting back in 2000 I got a lot of crud out of the drain hole. I also removed all the blow out discs. Surprising how much accumulates. It was very solid in places; I had to dig it out with rods. Not sure that flushing alone would have got it out. May be that's why my temps are down where they are.

Steve
Steve Gyles

Flushing alone probably would be very effective but I propose the following for that drain point, as required, for one thorough cleaning then just the usual service coolant drain and fresh refill -

. drain whilst poking around with wire
. running-water flush whilst poking around with wire until water runs clear
. refit drain plugs/taps refill and run engine something Barrs/Holts coolant system cleaners
. drain whilst poking around with wire
. running-water flush whilst poking around with wire until water runs clear
. running-water reverse-flush through drain aperture until water runs clear
. final running-water flush whilst poking around with wire until water runs clear.

Not as much effort as it may at first seem as it would be part of the overall coolant system cleaning - and again I'm not suggesting this would clear out much of the internal waterways but the same applied to the rest of the system does give the system a good clean out as a basis for regular servicing from then on.

Done fully along with some other general system external cleaning and maintenance and not only could there be a slight increase with cooling ability but also with the heater.
Nigel Atkins

I found the drain tap on the side of the engine block completely seized up - there is no way it would drain as was originally intended. After removing it,and cleaning the block, I replaced it with a copper bolt that was much easier to replace and, at a later date, to remove again.
If you need the part number of the bolt that fits, let me know and i'll dig it out
Graham V

I now remember who told me don’t worry that you can’t clear the route behind the tap as it very common. He has 30 plus years full time experience working with B series engines To be fair he was telling me after the my block had been cleaned out with the discs removed and you can’t get much better than that.

If you do get it clear the bolt idea is a good one.

Paul
Paul Dean

If you're doing any fluid change you want to get as much of the existing fluid (and muck and crud) out as possible otherwise the residue dilutes slightly the benefit of the fresh fluid.

The amount of residue left in on any change can be quite surprising especially when compared with the dry fill capacity but there'll always be some residue even on very thorough draining with siphoning and components and parts removal.

But as your dad or grandad would tell you, better out than in. :)
Nigel Atkins

Mine is fitted with the bolt. Cheaper than the tap! The clear out I did (as mentioned above) was after the block came back from the machine shop for bottom end overhaul including a rebore. I guess the lesson there is don't assume that they have cleaned out all the channels thoroughly. There was noticeable crud both at the top and bottom of the block. That's why I had to pull out the discs to get full access to it all.

As a post script the machine shop went out of business a short time later!

Steve
Steve Gyles

Good point Steve about not assuming that because the engine has been worked on (rebuilt, reconditioned, overhauled, cleaned) that the waterways will be clear.

My A-series engine was reconditioned but when I done my first straight drain & refill 3 months and 2,000 miles later I was surprised at the amount of crud that came out this lead me on to a thorough clean two years later whilst uprating and improving the existing cooling and heating systems.

Nigel Atkins

AR

Sorry I don’t know your first name but your blue block looks very similar to my dirty orange one. What I you block made from, as I said mine is a cut down kneeling pad.

Also in your photo it appears you have filled the gap between bonnet from and skin. Interesting, should we all be doing this?

Paul
Paul Dean

Hi Paul,

The block is made from a sleeping mat used by campers, so its about sleeping bag size cost about 6 quid in Halfords or any camping supplies shop. Its 1/4 inch thick foam material.

Basically its made by creating a radiator width square block made up of 7 layers stuck together with contact adhesive, and then trimmed to fit between the bonnet braces with a slight overlap at each end for tidiness. When glued to the bonnet, this thickness gives you a slight resistance when you try to shut the bonnet, but a firm push will get the lock to catch. Leave it for a couple of hours, maybe warm up the engine a bit and it will naturally assume the exact contours of the top of the radiator as per the photo. When it has taken the shape you can neaten the edges with additional strips.
My theory is that having the block there maintains a constant airflow especially in static traffic, as the air is forced through the radiator, not round or over the top. A test with my Zippo lighter shows the flame being sucked quite forcibly towards the radiator from the grill when stationary. I run at 180 all day long.
Hope this makes sense.

Regards
Alan
AR Terry

Like Alan’s my solution started life in Halfords but rather than a blue camping mat it was an orange kneeling mat. A couple of possible advantages are that I didn’t need to glue multiple layers and also I just cut the ends thinner so it just slots into the bonnet frame not requiring adhesive although I guess Alan’s version could do this too. Functionally it works the same.

I am afraid mine is rather grubby as it had served as a kneeling mat for a couple of years before I decided to use it for this experiment. The experiment has now lasted 2 years and I may sometime replace it by a new clean one. Also I can’t remember why it has a slot cut out but probably now irrelevant.

Unlike Alan I have never tested its effectiveness but certainly it doesn’t do any harm and I haven’t had a slow traffic overheating incident since fitting it. I never even see it in normal under bonnet work

I must replace it as a kneeling mat sometimes too!

Paul



Paul Dean

I bought mine from "Metal Mickey". http://www.sportscarmetalworks.com/mga/
Its in the catalogue under cooling system £12
Graham V

We are on the same page on this one Paul. Of course it could be made from one single block, it just so happened that I had the stuff in the garage so experimented. The main thing about this solution is the way the foam moulds permanently to the contour of the radiator, which was purely accidental. I'm pretty sure it fairly airtight, and it also prevents any vibration from the bonnet. Of course you can buy one as Graham says that may work just as well and look original. Just a bit of fun and it works.

Alan
AR Terry

An alternative to the felt block. Took only half an hour to make. Held in place with valcro along the radiator and easy to remove.


F Watson

Thats kind of neat, never would have thought of that as a solution. Another example of the innovation these great little cars create for there owners. Cant quite see from the photograph but doesn't it restrict the airflow through the top part of the radiator? Guess not.....
AR Terry

No as it angles back about 45 degrees. I also have an electric fan on the front of the radiator. It works well.
F Watson

FW. That's rather a natty mod. Makes you wonder why no one has come up with that before - including the manufacturers back then.

Does it show any difference to your operating temperatures?

That small shelf area would be very useful for Colyn Firth to store some more tools and spares.

Steve
Steve Gyles

FW
Yes I like it too. Very innovative
Graham V

I dont have any issues with temp. Even when its 40 degrees though I am not to keen to drive when it's that hot. Beautiful weather here in Perth just now around 20 to 24 degrees clear blue skies.
F Watson

NTG also stock the felt pad at £13 - but the VAT and P&P add £10 to that. But I also like FWs unique solution
Cam Cunningham

Cam,
I used three of the black felt blocks that the spare wheel sits on in the boot as a seal it seems to work well no over heating in France at temperatures of 40
degrees. I am using an original radiator just cleaned flushed when the car was rebuilt 15 years ago
Regards

David
D M SPEAK

This thread was discussed between 24/04/2019 and 11/06/2019

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